Johannes Plendl

Johannes "Hans" Plendl (6 December 1900 – 10 May 1991), German radar pioneer, was the scientist whose airplane navigation inventions made possible the early German bombing successes in World War II.

Plendl was born in 1900 in Munich, German Empire to parents from Northern Bavaria. His surname is most likely a truncated Bavarian dialect form of "Plendlein."

Plendl served briefly in the Imperial Kriegsmarine (Navy) during World War I. Shortly thereafter, Plendl began his career as a radio and beam engineer for Telefunken corporation.

His early research into meter-wave propagation and radar beams necessitated additional names for newly discovered levels of the Earth's atmosphere, and Plendl is generally credited with coining the term ionosphere. In the early 1930s, Plendl worked on developing the radio communications used in flights by civilian aircraft and the Hindenburg Zeppelin.

As Nazi Germany rearmed, Plendl and others saw the possibilities of using radio beams to guide bombers to their target, and they began to develop a system under the code name “X-System” (X-Verfahren). Using technology previously used for his Lorenz beam landing system, Plendl developed a system that would guide planes to their target, and which improved the accuracy of bombing at night or in poor weather conditions. This work was conducted for the German Airforce (Luftwaffe) at the Airforce Experimental Station (Erprobungstelle der Luftwaffe) at Rechlin, Germany, and also at Peenemunde. At the same time the system code named "Knickebein" was coined by the Telefunken electronics firm. Although it could use the Lorenz landing system for guidance, it was less accurate and more prone to jamming. Both systems employed transmitter towers on the English channel and the North Sea to transmit radar beams over targets in England. German bombers carried basic radar detectors and complex timing devices, also invented by Dr. Plendl, to lead them on the correct path and to guide the timing of the release of their bombs.

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